过硼酸钠结晶介稳区的测定

采用激光测定装置测定了过硼酸钠的溶解度和超溶解度,重点研究了过硼酸钠的溶解度、超溶解度以及结晶介稳区的变化规律,获得了过硼酸钠溶液的结晶介稳区,并用Apelblat方程对过硼酸钠的溶解度数据进行了关联。 研究了降温速率、搅拌速率、六偏磷酸钠及聚丙烯酸钠添加量对过硼酸钠介稳区宽度的影响规律。 研究结果表明,过硼酸钠溶解度随温度升高而增大,过硼酸钠的介稳区宽度在高温区较小而在低温区较大;降温速率的增大使过硼酸钠介稳区宽度变大,搅拌速率的增大使介稳区宽度变小;加入0.065%六偏磷酸钠和0.045%聚丙烯酸钠时获得的介稳区宽度最大。     

不同浓度KCl和NH4Cl溶液中H3BO3介稳区的性质

测定了H3BO3在0~25 ℃内于不同浓度KCl和NH4Cl溶液中的溶解度和超溶解度, 得到了H3BO3的介稳区宽度, 并推算出表观成核级数m, 给出了成核速率方程. 研究了KCl和NH4Cl对H3BO3介稳区性质的影响, 并对影响的机理进行了探讨. 结果表明, KCl使H3BO3介稳区向低温方向移动; NH4Cl使H3BO3介稳区向高温方向移动; 根据所得结论分析了KCl和NH4Cl在柴达木西部油田水析硼过程中的影响, 认为KCl和NH4Cl在蒸发过程中浓度的变化是造成硼分散析出而不能富集的因素之一.     

杀虫单介稳区宽度的理论计算

从晶体生长成核、动力学等几个方面出发,在Mersmann模型基础上建立了适合高粘度有机体系的介稳区宽度的理论计算模型,确立了计算程序和方法.结合“杀虫单”农药结晶过程的具体参数,计算和预测了工业结晶过程中介稳区的宽度.理论计算值与实验测定值较为接近.该方法可为工业结晶中过饱和度的选择提供参考.     

顶空进样GC-SIM-MS测定硝唑尼特中溶剂残留甲醇含量

利用气相色谱-选择离子监测质谱联用仪(GC-SIM-MS)测定硝唑尼特样品中溶剂残留甲醇的含量,顶空进样,温度为70℃,时间为20 min.SIM定量离子m/z 32,参考离子m/z 31,30和29.甲醇质量浓度在0.5~100μg/m L内呈良好的线性(R~2=0.999 92).方法相对标准偏差为2.49%~4.85%,样品加标回收在94.5%~102.8%之间,检测限为0.5μg/m L,符合定量分析的要求.     

Li+,K+/Cl-,CO32--H2O四元交互体系(298K)介稳相平衡的实验研究

我国西藏的扎布耶盐湖卤水以富含硼、锂、钾而闻名于世[1-2]。依据扎布耶盐湖卤水体系的主要成分,该卤水体系可简化Li K Na B4O72- CO32- Cl- SO42- H2O体系。针对西藏盐湖地处干旱、强日照特点,开展对扎布耶盐湖卤水体系的多温稳定及介稳相平衡研究,对于解释盐湖的演化及指     

Li~ ,Na~ //SO_4~(2-),B_4O_7~(2-)-H_2O交互四元体系288K介稳相平衡研究

采用等温蒸发法研究了四元体系Li ,Na //SO42-,B4O72--H2O288K介稳相平衡及平衡液相物化性质(密度、电导率、折光率、粘度和pH值),测定了该四元体系288K条件下介稳平衡溶液溶解度及物化性质。根据实验数据绘制了相应的介稳相图及物化性质组成图。研究发现:该体系介稳平衡中有复盐Li2SO·4Na2SO4形成。其介稳相图中有3个共饱和点,7条单变量曲线,平衡固相为:Li2SO·4H2O,Na2SO4,Li2SO·4Na2SO4,Li2B4O7·3H2O,Na2B4O·710H2O。复盐Li2SO·4Na2SO4和一水硫酸锂(Li2SO·4H2O)有较小的结晶区,而Li2B4O7·3H2O和Na2B4O7·10H2O有较大的结晶区;该四元体系介稳平衡条件下未发现Na2SO·410H2O的结晶区。     

五元体系Li+,Na+//CO32-,So42-,B4O72-H2O 288 K介稳相平衡研究

采用等温蒸发法研究五元体系Li+,Na+//CO32-,SO42-,B4O72--H2O 288 K介稳相平衡关系,测定在288 K条件下的介稳平衡溶液中各组分的溶解度和溶液密度,根据实验数据绘制相应的介稳平衡相图及密度组成图.研究结果表明该五元体系介稳相平衡中有复盐Na3Li(SO4)2·6H2O生成,其介稳相图中有4个共饱点,9条单变量曲线,6个Li2CO3饱和的结晶区分别为LiBO2·8H2O,Na284O7·10H2O,Na2CO3·10H2O,Na2SO4,Li2O4·H2O和复盐Na3Li(SO4)2·6H2O.     

Li＋, Na＋//SO42－, CO32－-H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li^＋, Na^＋// SO₄^2－, CO₃^2－-H₂O 288 K介稳相平衡及平衡液相的密度、电导率、折光率、粘度和pH值, 测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质. 根据实验数据绘制了相应的介稳相图. 研究发现: 该体系介稳平衡中有复盐Na₃Li(SO₄)₂•6H₂O形成. 其介稳相图中有3个共饱点, 7条单变量曲线, 平衡固相为: Li₂SO₄•H₂O, Na₂SO₄, Na₃Li(SO₄)₂•6H₂O, Li₂CO₃, Na₂CO₃•10H₂O. 复盐Na₃Li(SO₄)₂•6H₂O和一水硫酸锂(Li₂SO₄•H₂O)的结晶区较小, 而Li₂CO₃的结晶区最大; 该四元体系介稳平衡条件下未发现Na₂SO₄•10H₂O的结晶区.     

Li＋, Na＋//SO42－, CO32－-H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li^＋, Na^＋// SO₄^2－, CO₃^2－-H₂O 288 K介稳相平衡及平衡液相的密度、电导率、折光率、粘度和pH值, 测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质. 根据实验数据绘制了相应的介稳相图. 研究发现: 该体系介稳平衡中有复盐Na₃Li(SO₄)₂•6H₂O形成. 其介稳相图中有3个共饱点, 7条单变量曲线, 平衡固相为: Li₂SO₄•H₂O, Na₂SO₄, Na₃Li(SO₄)₂•6H₂O, Li₂CO₃, Na₂CO₃•10H₂O. 复盐Na₃Li(SO₄)₂•6H₂O和一水硫酸锂(Li₂SO₄•H₂O)的结晶区较小, 而Li₂CO₃的结晶区最大; 该四元体系介稳平衡条件下未发现Na₂SO₄•10H₂O的结晶区.     

Li+，Na+//SO42-，B4O72--H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li⁺，Na⁺//SO₄^2-，B₄O₇^2--H₂O 288 K介稳相平衡及平衡液相物化性质(密度、电导率、折光率、粘度和pH值)，测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质。根据实验数据绘制了相应的介稳相图及物化性质组成图。研究发现：该体系介稳平衡中有复盐Li₂SO₄·Na₂SO₄形成。其介稳相图中有3个共饱和点，7条单变量曲线，平衡固相为：Li₂SO₄·H₂O，Na₂SO₄，Li₂SO₄·Na₂SO₄，Li₂B₄O₇·3H₂O，Na₂B₄O₇·10H₂O。复盐Li₂SO₄·Na₂SO₄和一水硫酸锂(Li₂SO₄·H₂O)有较小的结晶区，而Li₂B₄O₇·3H₂O和Na₂B₄O₇·10H₂O有较大的结晶区；该四元体系介稳平衡条件下未发现Na₂SO₄·10H₂O的结晶区。     

Comparison of the Nucleation Kinetics Obtained from the Cumulative Distributions of the Metastable Zone Width and Induction Time Data

A linearized integral model based on classical nucleation theory is applied in this work to determine the interfacial energy and pre-exponential factor using a linear plot from the cumulative distributions of the metastable zone width (MSZW) data for some systems reported in the literature, including isonicotinamide, butyl paraben, dicyandiamide, and salicylic acid. Based on the same criterion for the nucleation point, the interfacial energy and pre-exponential factor are determined using the conventional linear regression method from the cumulative distributions of the induction time data for the same systems. The results indicate that the interfacial energy and pre-exponential factor calculated from the MSZW data are consistent with those calculated from the induction time for the studied systems.     

Solubility-Driven Isolation of a Metastable Nonagold Cluster with Body-Centered Cubic Structure

The conventional synthetic methodology for atomically precise gold nanoclusters by using reduction in solution offers only the thermodynamically most stable nanoclusters. Herein, a solubility-driven isolation strategy is reported to access a metastable gold cluster. The cluster, with the composition of [Au₉(PPh₃)₈]⁺ ( 1 ), displays an unusual, nearly perfect body-centered cubic (bcc) structure. As revealed by ESI-MS and UV/Vis measurements, the cluster is metastable in solution and converts to the well-known [Au₁₁(PPh₃)₈Cl₂]⁺ ( 2 ) within just 90 min. DFT calculations revealed that although both 1 and 2 are eight-electron superatoms, there is a driving force to convert 1 to 2 as shown by the increased cohesion and larger HOMO–LUMO energy gap of 2 . The isolation and crystallization of the metastable gold cluster were achieved in a biphasic reaction system in which reduction of gold precursors and crystallization of 1 took place concurrently. This synthetic protocol represents a successful strategy for investigations of other metastable species in metal nanocluster chemistry.     

K2B4O7-Na2B4O7-Li2B4O7-H2O 四元体系15℃介稳相平衡研究

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O15℃时的介稳相平衡及平衡液相的物化性质(密度,粘度,电导率,折光率,pH)。根据实验数据绘制了相图,相图中有一个共饱点E,三条单变度曲线E3F,E2F,E1F;三个平衡固相分别为：K2B4O7•4H2O,Na2B4O7•10H2O和Li2B2O4•16H2O;硼酸钾具有最大溶解度,硼酸钠具有最小溶解度。同时,根据试验数据绘制了组成－物化性质关系图,从图可见溶液的密度,粘度和折光率均随着溶液浓度的增大而逐渐增大,在共饱和点F处达到最大值,而溶液的pH值和电导率却随着溶液浓度的增大呈总体下降的趋势。     

Li+，Na+//CO32-，B4O72--H2O交互四元体系273 K介稳相平衡研究

我国青藏高原由于特殊的地理气候特点而盐湖众多,西藏境内的扎布耶盐湖卤水中锂、硼、钾浓度之高,在世界盐湖中也非常罕见[1-3].     

Metastable State of the Fc Fragment

The metastable state appearing at neutral pH in the Fc fragment after its brief incubation at pH 2.5 was studied using scanning microcalorimetry, high-flow sedimentation and fluorescence polarization. It was shown that the metastable state of the Fc fragment is characterised by smaller melting enthalpy of C_H2 domains as compared with that of the stable state which is explained by reduced interaction of C_H2 and C_H3domains. As seen from the decrease in the sedimentation coefficient, this leads to diminution of compactness of the Fc fragment molecule. The intramolecular motility of C_H2 domains increases judging by the fluorescence polarization data. This revised version was published online in July 2006 with corrections to the Cover Date.     

五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡研究

采用等温蒸发法研究了五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡关系,测定了该五元体系在288 K条件下的介稳平衡的溶解度和溶液密度,根据实验数据绘制了相应的介稳平衡相图和水图,相平衡研究结果表明该五元体系介稳相平衡中有复盐K_2SO_4·Li_2SO_4生成,其介稳相图(Li_2CO_3饱和)有4个共饱和点,9条单变量曲线,6个Li_2CO_3饱和的结晶区分别为LiBO_2·8H_2O,K_28_4O_7·4H_2O,K_2CO_3·3/2H_2O,K_2SO_4,Li_2SO_4·H_2O和复盐K_2SO_4·Li_2SO_4.     

Selective Formation of Metastable Ferrihydrite in the Chiton Tooth

Metastable precursors are thought to play a major role in the ability of organisms to create mineralized tissues. Of particular interest are the hard and abrasion‐resistant teeth formed by chitons, a class of rock‐grazing mollusks. The formation of chiton teeth relies on the precipitation of metastable ferrihydrite (Fh) in an organic scaffold as a precursor to magnetite. In vitro synthesis of Fh under physiological conditions has been challenging. Using a combination of X‐ray absorption and electron paramagnetic resonance spectroscopy, we show that, prior to Fh formation in the chiton tooth, iron ions are complexed by the organic matrix. In vitro experiments demonstrate that such complexes facilitate the formation of Fh under physiological conditions. These results indicate that acidic molecules may be integral to controlling Fh formation in the chiton tooth. This biological approach to polymorph selection is not limited to specialized proteins and can be expropriated using simple chemistry.